The present invention relates to a hub for magnetic tape reels or magnetic tape casettes, and more particularly to an improvement in a hub of such type provided with a tape clamp.
Typical clamps which have been conventionally used for retaining one end of a magnetic tape on the periphery of a hub of a reel or casette on which the tape is wound are those illustrated in FIGS. 1(a) and 1(b). These clamps comprise a web 1 and a pair of legs 2, 2 depending from the opposite ends of the web 1. The free ends of the legs 2 have stop ears which are adapted to be received in corresponding complementary slots of a hub (not shown). The clamps are integrally formed from a resilient but sufficiently rigid plastic material. In use, the legs 2 are bent inwardly with a suitable means (not shown) in the direction indicated by arrows and then inserted in a recess of the hub formed at a position along the periphery of the hub, with one end of a magnetic tape interposed between the clamp and the recess. More particularly, the web 1 of the clamp takes the form as illustrated in FIG. 2(a) prior to its insertion in the recess of the hub. Accordingly, the cross section as viewed from the line A--A of FIG. 2(a) will take the form as illustrated in FIG. 2(b) and, assuming that a tape 3 be wound on it, the wound tape 3 would be straight in its cross section. However, as the actual clamp is bent by inwardly urging the pair of legs before insertion of it into the recess, the web 1 is bent as shown in FIG. 3(a) and subjected to a non-uniform stress which causes the edges of the web 1 to upwardly curl as shown in FIG. 3(b). Accordingly, the tape 3 wound on it tends to curl along its edges as illustrated in FIG. 3, with a result that the tape is slightly stretched along its edges.
If this occurs, the recording or reproduction is necessarily adversely affected and such defects as leap in sound at spaced intervals of time, lowering of sound level and the like are encountered.